package com.bo.day20231201;

import java.util.Arrays;
import java.util.PriorityQueue;

/**
 * 堆排序
 *
 * @Author: gpb
 * @Date: 2023/12/5 11:05
 * @Description:
 */
public class HeapSort {

    public static void main (String[] args) {


        int[] heapArr = {5, 2, 3, 8, 9, 6, 7};
        heapSort(heapArr);
        // 默认小根堆
        PriorityQueue<Integer> heap = new PriorityQueue<>();
        heap.add(6);
        heap.add(8);
        heap.add(0);
        heap.add(2);
        heap.add(9);
        heap.add(1);

        while (!heap.isEmpty()) {
            System.out.println(heap.poll());
        }

        int testTime = 500000;
        int maxSize = 100;
        int maxValue = 100;
        boolean succeed = true;
        for (int i = 0; i < testTime; i++) {
            int[] arr1 = generateRandomArray(maxSize, maxValue);
            int[] arr2 = copyArray(arr1);
            heapSort(arr1);
            comparator(arr2);
            if (!isEqual(arr1, arr2)) {
                succeed = false;
                break;
            }
        }
        System.out.println(succeed ? "Nice!" : "Fucking fucked!");

        int[] arr = generateRandomArray(maxSize, maxValue);
        printArray(arr);
        heapSort(arr);
        printArray(arr);
    }


    /**
     * 排序逻辑：
     * 把arr数组维护成大根堆,大根堆每次弹出第一个数和数组最后一位交换
     *
     * @param arr
     */
    public static void heapSort (int[] arr) {
        if (arr == null || arr.length < 2) {
            return;
        }
        // 创建堆 从上往下
//        for (int i = 0; i < arr.length; i++) {
//            heapInsert(arr, i);
//        }
        // 从下往上创建堆
        for (int i = arr.length - 1; i >= 0; i--) {
            heapIfy(arr, i, arr.length);
        }
        // 排序
        int heapSize = arr.length;
        heapSize--;
        for (int i = 0; i < heapSize; heapSize--) {
            // 交换
            swap(arr, 0, heapSize);
            // 下沉,维护堆
            heapIfy(arr, 0, heapSize);
        }
    }


    /**
     * 建立堆
     *
     * @param arr
     * @param index
     */
    public static void heapInsert (int[] arr, int index) {
        while (arr[index] > arr[(index - 1) / 2]) {
            swap(arr, index, (index - 1) / 2);
            index = (index - 1) / 2;
        }
    }

    /**
     * 维护堆
     *
     * @param arr
     * @param index
     * @param heapSize
     */
    public static void heapIfy (int[] arr, int index, int heapSize) {
        int left = index * 2 + 1;
        while (left < heapSize) {
            int ans = left + 1 < heapSize && arr[left + 1] > arr[left] ? left + 1 : left;
            ans = arr[index] > arr[ans] ? index : ans;
            if (ans == index) {
                break;
            }
            swap(arr, index, ans);
            index = ans;
            left = index * 2 + 1;
        }
    }

    /**
     * 数组位置交换
     */
    public static void swap (int[] arr, int l, int r) {
        int t = arr[l];
        arr[l] = arr[r];
        arr[r] = t;
    }


    // for test
    public static void comparator (int[] arr) {
        Arrays.sort(arr);
    }

    // for test
    public static int[] generateRandomArray (int maxSize, int maxValue) {
        int[] arr = new int[(int) ((maxSize + 1) * Math.random())];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
        }
        return arr;
    }

    // for test
    public static int[] copyArray (int[] arr) {
        if (arr == null) {
            return null;
        }
        int[] res = new int[arr.length];
        for (int i = 0; i < arr.length; i++) {
            res[i] = arr[i];
        }
        return res;
    }

    // for test
    public static boolean isEqual (int[] arr1, int[] arr2) {
        if ((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)) {
            return false;
        }
        if (arr1 == null && arr2 == null) {
            return true;
        }
        if (arr1.length != arr2.length) {
            return false;
        }
        for (int i = 0; i < arr1.length; i++) {
            if (arr1[i] != arr2[i]) {
                return false;
            }
        }
        return true;
    }

    // for test
    public static void printArray (int[] arr) {
        if (arr == null) {
            return;
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
    }

}
